The invention relates to a digital transmultiplexer intended to convert a signal consisting of a plurality of telephony signals in TDM-format to a signal consisting of the said telephony signals in FDM-format and vice versa, the transmultiplexer comprising an arithmetic unit having on the one hand a first input and a first output for receiving and supplying, in digital form, the said signals in TDM-format and on the other hand a second input and a second output for receiving and supplying, in digital form, the said signals in FDM-format, the last-mentioned signals being located in a frequency band which is at least a frequency interval .DELTA.F removed from the zero frequency, .DELTA.F being the bandwidth of a telephony signal, the arrangement further comprising, to control the level of the signal in FDM-format, a digital generator for generating a pilot signal having the prescribed frequency, which is applied to the above-mentioned first input, the arrangement further comprising, to control the level of the received signals in FDM-format, a digital filter for selecting a pilot signal, the filter being connected to the above-mentioned first output.
Hereinafter "a signal in TDM-format" will be denoted TDM-signal for brevity. Correspondingly, "a signal in FDM-format" will be denoted FDM-signal.
Telephone networks in which TDM-systems as well as FDM-systems are used, utilize transmultiplexers for coupling these two different types of transmission systems to one another.